Method for production of fluorinated phenylenediamine

ABSTRACT

A method for the production of a fluorinated phenylenediamine is provided which comprises steps of reacting a diamide represented by the following formula with NaOCl at a molar ratio of the NaOCl to the diamide in the range of 2.0-6.0 and NaOH at a molar ratio of the NaOH to the diamide in the range of 1.8-6.0 is provided. According to this invention, the fluorinated phenylenediamine can be produced conveniently in a high yield.

TECHNICAL FIELD

This invention relates to a method for the production of a novelfluorinated phenylenediamine and more particularly to a method forproducing a fluorinated phenylenediamine in a high yield under moderatereaction conditions by a simple process.

BACKGROUND ART

A fluorinated phenylenediamines such as tetrafluoro-m-phenylenediamineis an important intermediate for the synthesis of pharmaceuticalpreparations, pesticides, and macromolecular compounds, and isparticularly useful as a raw material for a fluorine-containingpolyimide having a low dielectric constant and a low refractive index,absorbing light sparingly, and having excellent water repellency.

Tetrafluoro-m-phenylenediamine, for example, has been heretoforeproduced by the ammonolysis of hexafluorobenzene or pentafluoroanilineor by a process of reacting pentafluoroaniline with such a nucleophilicreagent as phthalic imide which can add an amino group thereby inducingthe substitution of an amino group for the fluorine atom and thenconverting the fluorine atom into the amino group. For example, Example3 of U.S. Pat. No. 3,461,135 discloses a method for producingtetrafluoro-m-phenylenediamine by reacting pentafluoroaniline withphthalimide potassium and redistilled dimethyl formamide, adding ethanoland hydrazine to the mixture, refluxing the resultant reaction solution,and subsequently adjusting the pH of the refluxed product with sodiumhydroxide to a weak alkali. This method, however, producestetrafluoro-m-phenylenediamine in such a low yield as 13.4% and,by-produces tetrafluoro-p-phenylenediamine which is an isomer thereof aswell as the tetrafluoro-m-phenylenediamine. As mentioned above, whentetrafluoro-m-phenylenediamine is to be produced,tetrafluoro-p-phenylenediamine is generally by-produced simultaneouslyat an approximate ratio in the range of 8:2 to 9:1.

The tetrafluoro-m-phenylenediamine aimed at, therefore, must beseparated and purified as by a process of distillation,recrystallization, column chromatography, and sublimation, for example.It is, however, extremely difficult to separate and purify thetetrafluoro-m-phenylenediamine and the by-producedtetrafluoro-p-phenylenediamine from each other.

JP-B-47-6,294 discloses a method for separating and purifyingtetrafluoro-m-phenylenediamine, which comprises acylating crudetetrafluoro-m-phenylenediamine containing tetrafluoro-p-phenylenediaminethereby precipitating the m-isomer in the form and subjecting theresidual filtrate further to diacylation and hydrolysis, and separatingthe m-isomer in the filtrate in the diacylated form. This method alsorequires to involve a process of separation and purification ortetrafluoro-m-phenylenediamine.

Another known method for producing tetrafluoro-m-phenylenediaminecomprises reacting tetrachloroisophthalonitrile in a benzonitrile mediumwith a fluorinating agent at a temperature in the range of 190-400° C.under spontaneous pressure (JP-B-63-5,023) thereby producingtetrafluoroisophthalonitrile, transforming this product to the form of adiamide (tetrafluoroisophthalamide), and subjecting the resultanttetrafluoroisophthalamide to Hoffmann rearrangement (“Synthesis offluoride compound and function,” pp. 204-205, published by CMC K.K. onMay 6, 1987).

Yet another known method for producing tetrafluoro-m-phenylenediaminecomprises reacting tetrafluoroisophthalic acid with sodium azide in astrong acid thereby producing tetrafluoro-m-phenylenediamine(JP-A-2001-226,329). In Example 2 thereof,tetrafluoro-m-phenylenediamine is produced in a high yield of 74.0%. InComparative Example 1 of this official gazette, a method for obtainingtetrafluoro-m-phenylenediamine which comprises usingtetrafluoroisophthalamide as a raw material, adding sodium hydroxide andbromide thereto thereby converting the group, —CONH₂, into a group,—CONHBr, extracting the resultant compound with isopropyl alcohol, andhydrolyzing the extract by the addition of hydrochloric acid isdescribed. This method comprises causing a mixed solution of sodiumhydroxide and bromine to act on the amide moiety oftetrafluoroisophthalamide thereby converting the amide into an amine byHoffmann rearrangement and eventually obtainingtetrafluoro-m-phenylenediamine. The yield of this product is 13.8%.

Since the Hoffmann rearrangement which is effected in the methoddescribed above uses a strong alkali such as sodium hydroxide in anexcess amount, however, the fluorine atoms are partially converted intoa hydroxyl group. On other words, as described in detail in ComparativeExample 1, the Hoffman rearrangement in a strong acid entails theproblem of lowering the yield of tetrafluoro-m-phenylenediamine as thetarget product.

DISCLOSURE OF THE INVENTION

Although the method described in Example 2 of the JP-A-2001-226,329 canattain a high yield, it gives rise to by-products copiously andnecessitates a subsequent intense purification process. Thus, a methodby which tetrafluoro-m-phenylenediamine can be produced with a highselectivity in a high yield without forming by-products, namely withoutentailing a process for separation and purification has beenenthusiastically demanded. The tetrafluoro-m-phenylenediamine, whencontaining by-products only in a small amount, manifests a small molarabsorption coefficient in a visible region and is particularly useful asan optical material. Therefore, a method for the production of suchtetrafluoro-m-phenylenediamine having a small molar absorptioncoefficient in a visible region has been demanded. Moreover, a strongneed has been felt for a method which permits the production oftetrafluoro-m-phenylenediamine by a moderate and simple process.

The present inventors, as a result of studying various methods for theproduction of tetrafluoro-m-phenylenediamine, have found that by theHoffmann rearrangement which converts an amide into an amine by causinga mixed solution of sodium hydroxide and chlorine to act on the amide,tetrafluoro-m-phenylenediamine can be produced fromtetrafluoroisophthalamide, and by adjusting the amounts of sodiumhydroxide and chlorine to be formulated in the above method, the yieldcan be enhanced and the occurrence of by-products can be repressedextremely, and thus the subsequent process for purification can besimplified, and the produced tetrafluoro-m-phenylenediamine can enjoyhigh purity. This invention has been perfected as a result.

According to this invention, simply by reacting a compound as a rawmaterial with NaOH and NaOX supplied in prescribed amounts, afluorinated phenylenediamine represented by the formula (2) shown hereinbelow can be produced in a high yield. The amount of NaOH to be used forthe reaction is smaller as compared with the amount contemplatedhitherto and the reaction, therefore, excels in safety.

In this invention, particularly by varying the temperature at twostages, the target compound can be produced while repressing theoccurrence of by-products without necessitating isolation of anyintermediate.

The compound obtained consequently has an extremely low molar absorptioncoefficient in a visible region, which indicates the occurrence ofby-products as impurities only in a small amount and permits thesubsequent purifying step to be simplified. Further, since this compoundhas high purity, it can be effectively used particularly for opticalapplications.

BEST MODE OF CARRYING OUT THE INVENTION

According to a first aspect of this invention, a method for theproduction of a fluorinated phenylenediamine represented by thefollowing formula (2), which comprises steps of reacting a diamiderepresented by the following formula (1) with NaOX [wherein X stands fora bromine atom (Br) or a chlorine atom (Cl)] at a molar ratio of theNaOX to the diamide (NaOX/diamide ratio) in the range of 2.0-6.0 andwith NaOH at a molar ratio of the NaOH to the diamide (NaOH/diamideratio) in the range of 1.8-6.0.

wherein in the formulas (1) and (2), Y stands for a hydrogen atom (H), abromine atom (Br), a chlorine atom (Cl), a fluorine atom (F), a C₁-C₅alkyl group optionally having a substituent, or a C₁-C₅ alkoxyl groupoptionally having a substituent, 1 is an integer in the range of 1-4, mis an integer in the range of 0-3, provided that the total number of 1and m (1+m) is 4.

This invention is aimed at producing a diamine represented by theformula (2) as the target compound by subjecting a diamide representedby the formula (1) to the so-called Hoffmann rearrangement whicheliminates carbon dioxide and forms an amine by the action of a mixedsolution of sodium hydroxide and chlorine. In this invention, attentionhas been directed to the fact that NaOCl is easily formed from a mixedsolution of sodium hydroxide and chlorine. Further, they have minutelystudied about the relationship between the amount of NaOCl and theamount of residual NaOH relative to the diamide represented by theformula (1) and the action of NaOCl and NaOH in the Hoffmannrearrangement, to find that by reacting the diamine with NaOX in such anamount as to give an NaOX/diamide ratio in the range of 2.0-6.0 and NaOHin such an amount as to give an NaOH/diamide ratio in the range of1.8-6.0, a fluorinated phenylenediamine represented by the formula (2)can be produced in a high yield. In this invention, it can becontemplates that a diamine of the formula (2) is formed from a diamideof the formula (1) by the following reaction, wherein X in the formulasstands for Cl. In the following formula, Y, m, and 1 are as defined inthe formula (1).

Specifically, a chlorine gas introduced into NaOH forms NaOCl, whichreacts with —CONH₂ to substitute a chlorine atom for the hydrogen atomof the amino group and to form a —CONHCl group. Subsequently, the—CONHCl group is converted into a —NCO group following therearrangement, which —NCO group is then hydrolyzed to form a —NH₂ group.This invention, therefore, is to provide a method for obtaining afluorinated phenylenediamine represented by the formula (2) whichcomprises reacting the diamide with NaOX at a NaOX/diamide ratio in therange of 2.0-6.0 and NaOH at a NaOH/diamide ratio in the range of1.8-6.0 thereby forming a compound represented by the following formula(3) and subsequently hydrolyzing this compound following the reaction ofrearrangement. In the formula (3), Y, m, and l are as defined in theformula (1) and X is derived from the NaOX used in the reaction. Now,this invention will be explained in detail below.

In the compound of the formula (1) and the compound of the formula (2)as the product which are used in this invention, m represents a numberof Y's bound to the benzene ring, which is an integer in the range of0-3, preferably 0 or 1.1 represents a number of fluorine atoms bound tothe benzene ring, which is an integer in the range of 1-4, preferably aninteger in the range of 2-4, and particularly preferably 3 or 4. In thiscase, the total number of 1 and m is 4 (1+m=4). When m is 2 or 3, namelywhen a plurality of Y's are present, the Y's may be identical with oneanother or different from one another.

The diamide represented by the formula (1) to be used particularlypreferably in this invention is a diamide which represented by thefollowing formula (4).

In the above formula (4), Y stands for a hydrogen atom (H), a bromineatom (Br), a chlorine atom (Cl), a fluorine atom (F), a C₁-C₅ alkylgroup optionally having a substituent, or a C₁-C₅ alkoxyl groupoptionally having a substituent, preferably F or Cl. In this preferableembodiment, a fluorinated phenylenediamine represented by the followingformula (5) wherein Y is F or Cl can be produced as the fluorinatedphenylenediamine represented by the formula (2).

This invention is characterized by the fact that the diamide representedby the formula (1) is reacted with NaOX at a NaOX/diamide ratio (asreduced to moles) in the range of 2.0-6.0, preferably 3.0-5.0, andparticularly preferably 3.5-4.5 and NaOH at a NaOH/diamide ratio (asreduces to moles) in the range of 1.8-6.0, preferably 2.0-4.0, andparticularly preferably 2.0-3.0. If the NaOX/diamide ratio is less than2.0, the yield would be lowered. Conversely, if this ratio exceeds 6.0,the amount of by-products formed would increase to make the producteasily colored. Particularly, since the diamine represented by theformula (1) contains at least one fluorine atom therein, it has apossibility of hydroxylating the fluorine atom on the benzene ring withan alkali and consequently increasing the amount of by-products formed.In consideration of this possibility, this invention has set the upperlimit of the NaOH/diamide ratio at 6.0. Conversely, if the NaOH/diamideratio is less than 1.8, the shortage would be at a disadvantage inlowering the yield.

The NaOX in the form of an anhydrous salt is an extremely unstablecompound. When a bromine gas or a chlorine gas is introduced into anaqueous sodium hydroxide solution, sodium hypochlorite is formed in anaqueous solution containing sodium chloride in accordance with thereaction of the following formula (6), which has been well-known.Cl₂+2NaOH═NaOCl+NaCl+H₂O  (6)

This invention, therefore, does not need to limit to the directintroduction of NaOX into the reaction system but may also use the NaOXprepared from NaOH and a bromine gas or a chlorine gas. The latter caseis preferable in terms of stability of NaOX. Incidentally, the amount ofNaOX to be formed can be calculated from the amount of the bromine orchlorine gas introduced. In this invention, the NaOX/diamide ratio andNaOH/diamine ratio as mentioned above can be satisfied by adjusting theamount of NaOH and the amount of bromine gas or chlorine gas added tothe diamide of the formula (1). For the purpose of reacting the diamiderepresented by the formula (1) with 2 mols of NaOX and 4 mols of NaOH,for example, 2 mols of bromide gas or chlorine gas may be introducedinto 8 mols of an aqueous NaOH solution. Since the relationship betweenthe occurrence of hydroxylation on the benzene ring and the amount ofsodium hydroxide has hitherto remained unknown, it has been customary tohave 1 mol of the diamide react with 12 mols of sodium hydroxide and 2.5mols of bromine, namely 2.5 mols of NaOX and 7.0 mols of NaOH have beenacted on 1 mol of the diamide, as demonstrated in Comparative Example 1cited in JP-A-2001-226,329. The reaction has resulted in formingby-products copiously and conspicuously lowering the yield to a level of13.8%. On the other hand, simply by controlling the amount of NaOH andthe amount of NaOX in the aforementioned ranges, this invention canimprove the yield significantly.

This invention can select other conditions in wide ranges so long as itcomprises a step of reacting the compound of the formula (1) with NaOXand NaOH in both amounts falling in each the range as mentioned above.The reaction is preferably performed at a temperature in the range of0-20° C., more preferably 0-10° C., and particularly preferably 0-5° C.It is inferred that the addition of NaOX and NaOH induces thesubstitution of the X of the NaOX for the hydrogen atom of the amide(—COHN₂) to efficiently form an intermediate having —CONHX representedby the formula (3). Since the compound represented by the formula (3) isextremely unstable, it is proper to perform the above reaction at atemperature of not higher than 20° C. in order to prevent the compoundfrom being decomposed. A temperature falling short of 0° C. is notproper for the reaction because the reaction solution freezes at such alow temperature. Generally, the reaction time may be sufficiently in therange of 0.5-3 hours, preferably 1-2 hours, and more preferably 1-1.5hours.

Subsequently, the —CONHX group in the intermediate is thermallyrearranged into a —NCO group in the reaction solution to form anisocyanate represented by the following formula (7).

In this invention, the isocyanate represented by the formula (7) may beisolated from the reaction solution as by extracting the reactionsolution with such a solvent as isopropyl ether and expelling thesolvent by distillation by means of an evaporator before the nextprocess. As typical examples of the solvent which is usable herein,halogenated hydrocarbons such as chloroform, methylene chloride, carbontetrachloride, chloroethane, dichloroethane, trichloroethane, andtetrachloroethane; hydrocarbons such as pentane, hexane, cyclohexane,and heptane; aromatic hydrocarbons such as benzene, toluene, and xylene,and ethers such as diethyl ether, isospropyl ether, tetrahydrofuran(THF), dioxane, diphenyl ether, benzyl ether, and tert-butyl ether maybe cited.

The isocyanate compound represented by the following formula (7) isconverted into a fluorinated phenylenediamine represented by the formula(2) by the hydrolysis with an acid or an alkali. In the formula (7), Y,m, and 1 are as defined in the formula (1).

The acid used to act on the compound of the formula (7) is preferred tobe a strong acid. As typical examples of the acid, concentrated sulfuricacid, trichloroacetic acid, sulfuric acid, polyphosphoric acids such aspyrophosphoric acid, triphosphoric acid, trimethaphosphoric acid, andtetrametaphosphoric acid, trifluoroacetic acid, trifluoroaceticanhydride, hydrochloric acid, fuming sulfuric acid, concentratedhydrochloric acid, hydrobromic acid, propionic acid, formic acid, nitricacid, and acetic acid; and the mixtures thereof such as, for example,trifluoroacetic acid-trifluoroacetic anhydride (the mixing ratio byweight in the range of 1:9-9:1, preferably 3:7-7:3), and the mixedsolution of trichloroacetic acid and sulfuric acid (the mixing ratio byweight in the range of 1:9-9:1, preferably 3:7-7:3) may be cited. Theseacids may be used either singly or in the form of a mixture of two ormore members. Among other acids cited above, at least one memberselected from the group consisting of concentrated sulfuric acid,polyphosplhoric acid, trifluoroacetic acid-trifluoroacetic anhydride,trichloroacetic acid, hydrochloric acid, concentrated hydrochloric acid,and sulfuric acid, particularly concentrated sulfuric acid and/orpolyphosphoric acid, is used particularly advantageously.

The amount of the acid to be used does not need to be particularlyrestricted but is only required to be sufficient for hydrolyzing the—NCO of the formula (7) into —NH₂. Generally, it is in the range of1.8-6.0 mols, preferably 2.0-3.0 mols, per mol of the intermediate ofthe formula (7). If this amount is less than 1.8 mols, the hydrolysiswould be attained incompletely to lower the yield. If it exceeds 6.0mols, the excess would possibly result in adding to the amount ofby-products formed.

Properly, the reaction is performed at a temperature exceeding 20° C.and not exceeding 100° C., preferably in the range of 40-80° C., andparticularly 60-80° C. If this temperature is not more than 20° C., thehydrolysis would be prevented from being completed or the rate ofreaction would be lowered, to impair the productivity. Conversely, ifthe temperature exceeds 100° C., the amount of by-products formed wouldincrease to lower the selectivity. The reaction time may be in the rangeof 0.5-3 hours, preferably 0.5-2 hours, and more preferably 1-1.5 hours.

When the compound of the formula (7) is hydrolyzed with an acid, theresultant compound of the formula (2) may possibly exist in the form ofan acid adduct. In the present specification, therefore, the fluorinatedphenylenediamine represented by the formula (2) is construed to includean acid adduct having an acid added to at least one of the diamines.Incidentally, since the acid adduct has considerable water solubility,the use of this compound in an aqueous solution proves a preferable modeof application. Meanwhile, the acid adduct can be removed by washingwith an alkali substance. This compound excels in solubility in anorganic solvent and is highly useful as a raw material for the synthesisof a macromolecular compound.

The alkalis which can be acted on the compound represented by theformula (7) include hydroxides, carbonates and phosphates of alkalimetals and alkaline earth metals, ammonia, and amine, for example. Inthis invention, sodium hydroxide, potassium hydroxide, calciumhydroxide, sodium carbonate, sodium hydrogen carbonate, calciumcarbonate, and an aqueous ammonia solution are particularly preferable.

The amount of the alkali to be used does not need to be particularlyrestricted but is only required to be sufficient for hydrolyzing the—NCO in the formula (7) into —NH₂. Generally, it is in the range of1.8-6.0 mols, preferably 2.0-3.0 mols, per mol of the compound of theformula (7). The reason for this range is that the amount, when fallingshort of 1.8 mols, would possibly render the hydrolysis incomplete andlower the yield and, when exceeding 6.0 mols, would add to the amount ofby-products formed.

In this invention, the action of the alkali on the compound of theformula (7) may be preferably carried out at a temperature exceeding 20°C. and not exceeding 100° C., more preferably in the range of 40-80° C.,and particularly preferably 60-80° C. If this temperature falls short of20° C., the rearrangement would be prevented from being completed or therate of reaction is lowered, to impair the productivity. Conversely, ifthe temperature exceeds 100° C., the excess would possibly add to theamount of by-products formed and degrade the selectivity. The reactiontime may be in the range of 0.5-3 hours, preferably 0.5-2 hours, andmore preferably 1-1.5 hours.

The fluorinated phenylenediamine represented by the formula (2) which isconsequently obtained may be isolated from the reaction solution andfurther purified. As means to effect this purification, distillation,recrystallization, sublimation, salting out, silica gel columnchromatography, and treatment with an activated carbon may be cited.Since the by-products is generated only in a small amount in thisinvention, the purification can be carried out fully satisfactorily bysuch a simple operation as by the treatment with activated carbon.

In this invention, since the fluorinated phenylenediamine represented bythe formula (2) is finally obtained by reacting the diamide representedby the formula (1) with NaOH and NaOX at a temperature in the range of0-20° C. thereby obtaining the compound represented by the formula (3)and further treating this compound with an alkali at a temperatureexceeding 20° C. and not exceeding 100° C., it means that thefluorinated phenylenediamine represented by the formula (2) can beproduced simply and easily by incorporating the step of reacting thediamide represented by the formula (1) with NaOX at a NaOX/diamine ratioin the range of 2.0-6.0 and NaOH at a NaOH/diamide ratio in the range of1.8-6.0 and by changing the temperature in two stages. In this respect,this invention relates tp a method for the production of a fluorinatedphenylenediamine represented by the formula (2), which is characterizedby incorporating therein a step of reacting a diamide represented by theformula (1) with NaOX at a NaOX/diamide ratio in the range of 2.0-6.0and NaOH at a NaOH/diamide ratio in the range of 1.8-6.0, and byreacting the diamide with the NaOX and NaOH at a temperature in therange of 0-20° C. and subsequently heating the resultant reactionproduct to a temperature exceeding 20° C. and not exceeding 100° C.

By adjusting the temperature in the two stages as mentioned above, afluorinated phenylenediamine represented by the formula (2) can beproduced by an easy and simple method in a very high yield.

Thus, at the first stage, the reaction is performed at a temperaturepreferably in the range of 0-20° C., more preferably 0-10° C., andparticularly preferably 0-5° C. and then at the second stage, thereaction is performed by heating at a temperature preferably exceeding20° C. and not exceeding 100° C., more preferably falling in the rangeof 40-80° C., and particularly preferably 60-80° C. The first stageforms the —CONHX by the substitution of the X of the NaOX for thehydrogen atom of the amide (—CONH₂) of the formula (1) and, therefore,corresponds to the step of forming the compound of the formula (3). Thereaction is performed at a temperature which is set so as to be nothigher than 20° C. for the purpose of preventing the —CONHX, anextremely unstable group, from being decomposed and also be not lowerthan 0° C. for the purpose of preventing the reaction solution fromfreezing. The reaction time of the first stage may be in the range of0.5-3.0 hours, preferably 0.5-2.0 hours, and more preferably 1.0-1.5hours.

The second stage corresponds to the step of converting the —CONHX intothe —NCO by the rearrangement and further converting the —NCO into the—NH₂ via the hydrolysis. As a result, the fluorinated phenylenediamineof the formula (2) would be formed from the compound of the formula (3).If the temperature falls short of 20° C., the rearrangement would beprevented from being completed or the rate of reaction would decrease,to impair the productivity. Conversely, if the temperature exceeds 100°C., the excess would possibly add to the amount of by-products formedand degrade the selectivity. The reaction time of the second stage maybe in the range of 0.5-3.0 hours, preferably 0.5-2.0 hours, and morepreferably 1.0-1.5 hours. According to this method, in the process forproducing the fluorinated phenylenediamine represented by the formula(2) by using the compound of the formula (1) as the raw material, thetarget compound can be produced without isolating any intermediate.Moreover, in consequence of controlling the amount of NaOH to be used,the target compound can be produced in an extremely high yield.

Incidentally, the method of adjusting the temperature at the two stagesas described above may be modified by adjusting the temperature at threestages or by gradually elevating the temperature. One modification maycomprise performing the reaction at a temperature in the range of 0-20°C. for one hour, then at a temperature in the range of 20-60° C. for 0.5hour, and further at a temperature in the range of 60-80° C. for onehour, for example.

After the reaction which follows the second stage of heating iscompleted, it is proper that the resultant reaction solution be adjustedto a pH in the range of 9-14 by the addition of an alkali. When thereaction solution is acid by the hydrolysis, the HX (wherein X isderived from the NaOX added during the reaction) in the reactionsolution, for example, is linked as an acid adduct to the amino group ofthe fluorinated phenylenediamine represented by the formula (2). As aresult, the compound obtained consequently becomes water-soluble. Theacid adduct can be removed by adding an alkali to the compound andwashing the compound with the alkali.

One of the characteristics of this invention is that the fluorinatedphenylenediamine represented by the formula (2) as the target compoundcan be produced conveniently in a high yield without any separation ofan intermediate by using the diamide represented by the formula (1) asthe starting raw material and reacting the diamide with specific amountsof NaOX and NaOH. The fluorinated phenylenediamine of the formula (2)which is consequently obtained contains by-products only in a smallamount and thus no subsequent steps of purifying the product to a highdegree are not necessary. The fluorinated phenylenediamine representedby the formula (2) of this invention a molar absorption coefficient at awavelength of 450 nm in a visible region, as measured with aspectrophotometer, preferably of not more than 2.5 (1/mol·cm), morepreferably not more than 2.0 (1/mol·cm). The fluorinatedphenylenediamine which is obtained by the method of production of thisinvention may be particularly useful as an optical material because ithas a small molar absorption coefficient in a visible region.

The fluorinated phenylenediamine of the formula (2) so obtained may beisolated from the reaction solution and purified. The means for thispurification includes distillation, recrystallization, sublimation,salting out, silica gel column chromatography, and treatment with anactivated carbon, for example.

In this invention, polyamide can be produced by using as a raw materialtherefor the fluorinated phenylenediamine which is obtained by themethod as described above. Though the method of production does not needto be particularly limited, polyamic acid represented by the formula (9)can be produced by reacting the fluorinated phenylenediamine obtained bythe aforementioned method with tetracarboxylic acid represented by thefollowing formula (8), the acid anhydride or acid chloride thereof, orthe ester thereof in an organic solvent in accordance with the methodsdisclosed in Japanese Patent No. 3,082,879 and JP-A-2003-26,799, forexample.

(wherein X′ stands for a tetravalent organic group)>

(wherein Y stands for H, Br, Cl, F, a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group).

For example, the reaction disclosed in JP-A-2003-26,799 may be performedunder the same reaction conditions as specified therein while using thefluorinated phenylenediamine according to this invention in place of the1,3-diaminobenzene derivative disclosed in JP-A-2003-26,799. Similarly,the reaction disclosed in Japanese Patent No. 3,082,879 while using thefluorinated phenylenediamine according to this invention in place of thediamine specified in Paragraph [0014] thereof.

As typical examples of the tetracarboxylic acid represented by theformula (8) and used advantageously herein, tetracarboxylic acids whichare disclosed in Paragraphs [0040]-[0049] of JP-A-2003-26,799, inParagraph [0013] of Japanese Patent No. 3,082,879, and in Paragraphs[0043]-[0046] of JP-A-2003-313,293 may be cited. These tetracaraboxylicacids, acid anhydrides or acid chlorides thereof, or esters thereof maybe properly used. The typical examples of the substituent, “X′”, in theformula (8) are as follows. To be specific, “X′” may stand for atetravalent aliphatic organic group derived from cyclic alkyls, chainalkyls, olefins, and glycols; a tetravalent aromatic organic groupderived from benzene biphenyl, biphenyl ether, bisphenyl benzene, andbisphenoxy benzene; and a tetravalent organic group such ashalogen-containing aliphatic and aromatic organic groups. Among othersubstituents cited above, tetravalent aromatic organic groups, morepreferably tetravalent halogen-containing aromatic organic groups arepreferable as the “X′” in the formula (8). In these aromatic organicgroups, particularly preferable tetravalent organic groups as the “X′”in the formula (8) are such tetravalent organic groups as represented bythe following formulas.

In the above formulas which represent the preferable organic groups asthe “X′”in the formula (8), R¹ and R² stand for a halogen atom, namely afluorine, chlorine, bromine, or iodine atom, preferably a fluorine orchlorine atom, and most preferably a fluorine atom. In this case, R¹ andR² may be identical with each other or different from each other. When aplurality of R¹'s and/or R²'s are present in each the relevant benzenerings (namely, when n and/or n′ is 2 or 3), they may be identical witheach other or different from each other in the relevant benzene rings.Then, n and n′ represent numbers of R¹ and R² bound to the relevantbenzene rings and specifically are integers of in the range of 1-3. Theintegers, n and n′, are preferably 3 because no C—H bonds are desirablypresent in consideration of such factors as the heat resistance,resistance to chemicals, water repellency, and low dielectric property.In this case, n and n′ may be an identical number or different numbers.

In the formula as mentioned above, Z stands for a connector or adivalent group represented by the following formulas.

Among these Z's, Z preferably stands for a connector or a divalentgroups represented by the following formulas.

In the foregoing formulas representing the substituent “Z”, Y′, and Y″stand for a halogen atom, namely a fluorine, chlorine, bromine, oriodine atom, preferably a fluorine or chlorine atom, and most preferablya fluorine atom. When Y′ and Y″ are both present in the formularepresenting “Z”, Y′ and Y″ may be identical with each other ordifferent from each other. When Y′ and Y″ are respectively present in aplurality in the relevant benzene rings (namely, when r and/or r′ is aninteger of 2-4), each Y′ and Y″ may be identical with each other ordifferent from each other. Then, r and r′ respectively represent anumber of Y′ and Y″ bound to the relevant benzene rings, respectively,and are integers in the range of 1-4, preferably 2-4. Most preferably,the integers, r and r′, are preferably 4 because no C—H bonds aredesirably present in consideration of such factors as the heatresistance, resistance to chemicals, water repellency, and lowdielectric property. In this case, r and r′ may be an identical numberor different numbers.

Incidentally, the terminal of the polyamic acid contemplated by thisinvention is considered to be either an amine terminal or an acidderivative terminal, though it is variable with the amounts of thefluorinated phenylenediamine and the tetracarboxylic acid derivative tobe added (molar ratio).

When the polyamic acid is cyclized by heating, the polyimide representedby the following formula (10) can be produced.

(wherein Y stands for H, Br, Cl, F, a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group).

The method of production thereof does not need to be particularlylimited. The reaction in accordance with any of the methods disclosed inJapanese Patent No. 3,082,879, JP-A-2003-26,799, and JP-A-2003-313,293can be carried out, for example. The terminal of the polyimidecontemplated by this invention is considered to be an amine terminal oran acid derivative terminal.

Now, this invention will be described more specifically below withreference to working examples.

SYNTHESIS EXAMPLE 1

In a three neck flask having an inner volume of 1 liter, 63.08 g ofpurified water and 1048.74 g of 98% sulfuric acid were placed andstirred to prepare a 92% sulfuric acid solution. The resultant solutionwas heated to 80° C. and then kept cooled to keep the inner temperatureof the flask in the range of 90 to 100° C. and 350.13 g (1.75 mols) oftetrafluoroisopthalonitrile was added piece meal to the cooled solution.After completion of this addition, the reaction solution in the flaskwas stirred for one hour while the inner temperature of the flask waskept at 90 to 100° C. and then the reaction solution was cooled to 30°C. Then, 1400 g of ice was placed in a beaker having an inner volume of3 liters and the reaction solution was gently added dropwise to the iceso as to keep the inner temperature of the beaker from exceeding 60° C.After the completion of the dropwise addition, the mixture was cooled to20° C. and then kept at 20° C. for one hour. A white solid which wasprecipitated was separated by filtration, washed with 1000 g of water,and then dried to obtain 407.95 g (1.73 mols) oftetrafluoroisophthalamide as a white solid (yield 98.8%).

SYNTHESIS EXAMPLE 2

By repeating the procedure of Synthesis Example 1 while using 757.92 g(3.5 mols) of 5-chloro-2,4,6-trifluoroisophthalonitrile in place oftetrafluoroisophthalonitrile, 876.45 g (3.47 mols) of5-chloro-2,4,6-trifluoroisophthalamide was obtained as a white solid(yield 99.0%)

EXAMPLE 1

In a three neck flask having an inner volume of 1 liter, 197 g of waterand 26.91 g (168.2 mmols) of 25% NaOH were placed and cooled to 0° C.Further, 83.53 g (280 mmols) of 24.95% NaClO was additionally placed inthe flask and cooled to 0° C. Then, 16.7652 g (71 mmols) oftetrafluoroisophthalamide obtained in Synthesis Example 1 was graduallyadded to the flask. After the completion of the addition, the resultantmixture was stirred at a temperature of not higher than 5° C. for onehour. Then, the resultant reaction solution was diluted by the additionof 390 g of water, heated to 60-70° C. and stirred for one hour, andthen cooled to 30° C. After the completion of cooling, the reactionsolution was adjusted to pH 9 by the addition of 25% NaOH. This solutionand 260 g of toluene added thereto were stirred together for 15 minutesfor the sake of extraction. Thereafter, the resultant mixture was leftstanding for 10 minutes to effect the separation thereof. When the uppertoluene layer was dried to a solid with an evaporator, 11.60 g of areddish brown solid was obtained. This reddish brown solid and toluenewere added together so as to give a total amount of 22.4 g and thenheated to a temperature of not lower than 80° C. to completely dissolvethe solid therein. The resultant solution was gradually cooled to 15° C.and then left standing at 15° C. for one hour. A brown solidconsequently precipitated was separated by filtration, washed with 10 gof cold toluene, and then dried to obtain 7.94 g (44.1 mmols) oftetrafluoro-m-phenylenediamine as a brown solid (yield 63%). The purityof this product was determined by gas chromatography to find to be99.99%.

EXAMPLE 2

In a three neck flask having an inner volume of 5 liters, 650 g of waterand 153.6 g (960 mmols) of 25% NaOH were placed and cooled to 0° C.Further, 960.52 g (1600 mmols) of 12.40% NaClO was additionally placedand cooled to 0° C. Then, 95.65 g (405.1 mmols) oftetrafluoroisophthalamide obtained in Synthesis Example 1 was graduallyadded while the inner temperature of the flask kept at a level of nothigher than 5° C. After the completion of the addition, the resultantmixture was stirred at a temperature of not higher than 5° C. for onehour. Then, the resultant reaction solution was diluted by the additionof 2210 g of water, heated to 60-70° C. and stirred for one hour, andcooled to 30° C. After the completion of the cooling, when the reactionsolution was adjusted to pH 14 by the addition of 25% NaOH, a brownsolid was precipitated. When the solid thus precipitated was separatedby filtration, washed with purified water, and then dried, 54.4 g (302.1mmols) of tetrafluoro-m-phenylenediamine was obtained as a brown solid(yield 75.5%). The purity of this product was determined by gaschromatography to find to be 99.99%.

EXAMPLE 3

In a three neck flask having an inner volume of 1 liter, 100 g of waterand 23.07 g (144 mmols) of 25% NaOH were placed and cooled to 0° C.Further, 144.54 g (240 mmols) of 12.36% NaClO was placed additionallyand cooled to 0° C. Then, 15.4171 g (61 mmols) of5-chloro-2,4,6-trifluoroisophthalamide obtained in Synthesis Example 2was gradually added while the inner temperature of the flask kept tobelow 5° C. After the completion of this addition, the resultant mixturewas stirred at a temperature of not higher than 5° C. for one hour.Then, the resultant reaction solution was diluted by the addition of 345g of water, heated to 60-70° C., stirred for one hour, and then cooledto 30° C. After the completion of the cooling, the reaction solution wasadjusted to pH 9 by the addition of 25% NaOH. This solution and 260 g oftoluene added thereto were stirred together for 15 minutes to effect theextraction. The resultant reaction solution was left standing for 10minutes to effect the separation of the solution. When the upper toluenelayer was dried to a solid with an evaporator, 10.61 g of a reddishbrown solid was obtained. This reddish brown solid was added withtoluene so as to give a total amount of 21.47 g and heated to atemperature of not lower than 80° C. to completely dissolve the solidtherein. The resultant solution was gradually cooled to 15° C. and leftstanding at 15° C. for one hour. The brown solid consequentlyprecipitated was separated by filtration, washed with 10 g of coldtoluene, and dried to obtain 9.51 g (48.4 mmols) of5-chloro-1,4,6-trifluoro-m-phenylenediamine as a brown solid (yield80.7%). The purity of this product was determined by gas chromatographyto find to be 99.81%.

EXAMPLE 4

0.3 g of tetrafluoro-m-phenylenediamine obtained in Example 1 wasdissolved in acetonitrile so as to give a total amount of 3 g. When thissolution was analyzed with a spectrophotometer to determine theabsorbance in a visible region, the molar absorbance coefficient at awavelength of 450 nm was found to be 1.649 (1/mol·cm).

EXAMPLE 5

A solution of 5 g of tetrafluoro-m-phenylenediamine obtained in Example1 in 70 g of toluene and 0.15 g of activated carbon added thereto werestirred together at room temperature for one hour. After the completionof the stirring, the resultant mixture was filtered to separate theactivated carbon therefrom. When the filtrate was dried to a solid withan evaporator, 4.64 g of tetrafluoro-m-phenylenediamine was obtained asa white solid. 0.3 g of this white solid was dissolved in acetonitrileto give a total amount of 3 g. When the solution was analyzed with aspectrophotometer to determine the absorbance in a visible region, themolar absorbance coefficient at a wavelength of 450 nm was found to be0.013 (1/mol·cm).

EXAMPLE 6

0.3 g of 5-chloro-1,4,6-trifluoro-m-phenyleneidamine obtained in Example2 was dissolved in acetonitrile to give a total amount of 3 g. When thissolution was analyzed with a spectrophotometer to determine theabsorbance in a visible region, the molar absorbance coefficient at awavelength of 450 nm was found to be 1.802 (1/mol·cm).

EXAMPLE 7

A three neck flask having an inner volume of 50 ml was charged with 2.25g (12.5 mmols) of tetraflfuoro-m-phenylenediamine obtained in Example 1,7.28 g (12.5 mmols) of4,4′-[(2,3,5,6-tetr4aflfuoro-1,4-phenylene)bis(oxy)]bis(3,5,6-trifluorophthalicanhydride), and 16 g of N,N-dimethylacetamide. This mixed solution wasstirred in an atmosphere of nitrogen at room temperature for 30 minutesto form a homogeneous solution. The resultant solution was then leftstanding for four days to obtain a light yellow highly viscous polyamicacid solution.

EXAMPLE 8

A three neck flask having an inner volume of 50 ml was charged with 2.25g (12.5 mmols) of tetrafluoro-m-phenylenediamine obtained in Example 5,7.28 g (12.5 mmols) of4,4′-[(2,3,5,6-tetrafluoro-1,4-phenylene)bis(oxy)]bis(3,5,6-trifluorophthalicanhydride), and 16 of of N,N-dimethyl acetamide. The resultant mixedsolution was stirred in an atmosphere of nitrogen at room temperaturefor 30 minutes to form a homogeneous solution. The resultant solutionwas further left standing for four days to obtain a light yellow highlyviscous polyamic acid solution.

EXAMPLE 9

A three neck flask having an inner volume of 50 ml was charged with 2.46g (12.5 mmols) of 5-chloro-2,4,6-trifluoro-m-phenylenediamine obtainedin Example 3, 7.28 g (12.5 mmols) of4,4′-[(2,4,5,6-tetrafluoro-1,4-phenylene)bis(oxy)]bis(3,5,6-trifluorophthalicanhydride), and 16 g of N,N-dimethyl acetamide. The resultant mixedsolution was stirred in an atmosphere of nitrogen at room temperaturefor 30 minutes to form a homogeneous solution. This solution was furtherleft standing for four days to obtain a light yellow highly viscouspolyamic acid solution.

EXAMPLE 10

The polyamic acid obtained in Example 7 was applied by spin coating on asilicon substrate having a diameter of 4 inches. When the coating washeated in an atmosphere of nitrogen at 70° C. for two hours, at 160° C.for one hour, at 250° C. for 30 minutes, and further at 350° C. for onehour, a polyimide film was formed on the silicon substrate.

EXAMPLE 11

The polyamic acid obtained in Example 8 was applied by spin coating on asilicon substrate having a diameter of 4 inches. When the coating washeated in an atmosphere of nitrogen at 70° C. for two hours, at 160° C.for one hour, at 250° C. for 30 minutes, and further at 350° C. for onehour, a polyimide film was formed on the silicon substrate.

EXAMPLE 12

The polyamic acid obtained in Example 9 was applied by spin coating on asilicon substrate having a diameter of 4 inches. When the coating washeated in an atmosphere of nitrogen at 70° C. for two hours, at 160° C.for one hour, at 250° C. for 30 minutes, and further at 350° C. for onehour, a polyimide film was formed on the silicon substrate.

COMPARATIVE EXAMPLE 1

In a three neck flask having an inner volume of 50 ml, 4.0 g (101.84mmols) of sodium hydroxide and 25 ml of deionized water were placed.Then, 1.09 ml (21.18 mmols) of bromine was added dropwise to the flaskover a period of 15 minutes while the flask kept cooled with an icebath. Then, 2.0 g (8.47 mmols) of tetrafluoroisophthalamide wasadditionally placed. The resultant mixed solution was refluxed andstirred for 20 hours, cooled to room temperature, then extracted withisopropyl ether, washed with deionized water, then dried over magnesiumsulfate, and distilled to expel the solvent with an evaporator to obtain2.42 g of a brown solid. In a three neck flask having an inner volume of50 ml, this solid and 20 mg of 20% hydrochloric acid were placedtogether, refluxed and stirred for five hours. The solution was cooledto room temperature. In a beaker having an inner volume of 500 ml, icewater was placed and the cooled solution was poured into the ice waterand then an aqueous sodium hydroxide solution was added there todropwise till the pH value reached 14. Then, the resultant reactionsolution was extracted with chloroform, washed with deionized water,dried over magnesium sulfate, and distilled to expel the solvent with anevaporator to obtain 0.25 g of a reddish brown solid (yield 16.4%).

0.1 g of tetrafluoro-m-phenylenediamine thus obtained was dissolved inacetonitrile so as to give a total amount of 1 g. When the solution wasanalyzed with a spectrophotometer to determine the absorbance in avisible region, the molar absorption coefficient at a wavelength of 450nm was found to be 4.124 (1/mol·cm).

COMPARATIVE EXAMPLE 2

The solution of 0.15 g of tetrafluoro-m-phenylenediamine obtained inComparative Example 1 in 2.1 g of toluene and 0.0045 g of activatedcarbon added thereto were stirred together at room temperature for onehour. After the completion of the stirring, the resultant mixture wasfiltered to remove the activated carbon. When the filtrate was dried toa solid with an evaporator, 0.13 g of tetrafluoro-m-phenylenediamine wasobtained as a brown solid. 0.13 g of this brown solid was dissolved inacetonitrile so as to give a total amount of 1.3 g. When this solutionwas analyzed with a spectrophotometer to determine the absorbance in avisible region, the molar absorption coefficient at a wavelength of 450nm was found to be 3.093 (L/mol-cm).

COMPARATIVE EXAMPLE 3

The reaction of Hoffmann rearrangement was tried by following theprocedure of Example 1 while using 41.79 g (140 mmols) of 24.95% NaClOin place of 83.53 g (280 mmols) of 24.95% NaClO. As a result, 0.54 g (3mmols, yield 4.3%) of tetrafluoro-m-phenylenediamine was obtained. Thepurity of this product was determined by gas chromatography to find tobe 98.30%.

INDUSTRIAL APPLICABILITY

This invention is to provide a fluorinated phenylenediamine manifestinglow absorption in a visible region and suitable for an optical material,polyamic acid using the diamine as a raw material, and a method for theconvenient production of polyimide. The products according to thisinvention are useful for the production of an optical material.

1. A method for the production of a fluorinated phenylenediaminerepresented by the following formula (2), which comprises steps ofreacting a diamide represented by the following formula (1) with NaOX[wherein X stands for a bromine atom (Br) or a chlorine atom (Cl)] at amolar ratio of the NaOX to the diamide (NaOX/diamide ratio) in the rangeof 2.0-6.0 and NaOH at a molar ratio of the NaOH to the diamide(NaOH/diamide ratio) in the range of 1.8-6.0.

wherein in the formulas (1) and (2), Y stands for a hydrogen atom (H), abromine atom (Br), a chlorine atom (Cl), a fluorine atom (F), a C₁-C₅alkyl group optionally having a substituent, or a C₁-C₅ alkoxyl groupoptionally having a substituent, 1 is an integer in the range of 1-4, mis an integer in the range of 0-3, provided that the total number of 1and m (1+m) is
 4. 2. A method according to claim 1, wherein said diamideis reacted with NaOX and NaOH at a temperature in the range of 0-20° C.and the resultant reaction product is heated at a temperature exceeding20° C. and not exceeding 100° C.
 3. A method according to claim 1,wherein said diamide is a diamide represented by the following formula(4) and said phenylenediamine is a phenylenediamine represented by thefollowing formula (5).

wherein in the formulas (4) and (5), Y stands for a hydrogen atom (H), abromine atom (Br), a chlorine atom (Cl), a fluorine atom (F), a C₁-C₅alkyl group optionally having a substituent, or a C₁-C₅ alkoxyl groupoptionally having a substituent.
 4. A method according to claim 1,wherein the molar absorption coefficient of the fluorinatedphenylenediamine represented by the formula (2) at a wavelength of 450nm is not more than 2.5 (1/mol·cm).
 5. A method for the production of apolyamic acid represented by the formula (9), which comprises reactingthe fluorinated phenylenediamine produced by the method set forth inclaim 1 with tetracaraboxylic acid represented by the formula (8), theacid anhydride or acid chloride thereof, or the ester thereof in anorganic solvent.

wherein X′ stands for a tetravalent organic group,

wherein Y stands for a hydrogen atom (H), a bromine atom (Br), achlorine atom (Cl), a fluorine atom (F), a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group.
 6. A method for theproduction of polyimide represented by the formula (10), which comprisescyclizing by heating the polyamic acid produced by the method set forthin claim 5:

wherein Y stands for a hydrogen atom (H), a bromine atom (Br), achlorine atom (Cl), a fluorine atom (F), a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group.
 7. A method according toclaim 2, wherein said diamide is a diamide represented by the followingformula (4) and said phenylenediamine is a phenylenediamine representedby the following formula (5).

wherein in the formulas (4) and (5), Y stands for a hydrogen atom (H), abromine atom (Br), a chlorine atom (Cl), a fluorine atom (F), a C₁-C₅alkyl group optionally having a substituent, or a C₁-C₅ alkoxyl groupoptionally having a substituent.
 8. A method according to claim 2,wherein the molar absorption coefficient of the fluorinatedphenylenediamine represented by the formula (2) at a wavelength of 450nm is not more than 2.5 (1/mol·cm).
 9. A method according to claim 3,wherein the molar absorption coefficient of the fluorinatedphenylenediamine represented by the formula (2) at a wavelength of 450nm is not more than 2.5 (1/mol·cm).
 10. A method according to claim 7,wherein the molar absorption coefficient of the fluorinatedphenylenediamine represented by the formula (2) at a wavelength of 450nm is not more than 2.5 (1/mol·cm).
 11. A method for the production of apolyamic acid represented by the formula (9), which comprises reactingthe fluorinated phenylenediamine produced by the method set forth inclaim 2 with tetracaraboxylic acid represented by the formula (8), theacid anhydride or acid chloride thereof, or the ester thereof in anorganic solvent.

wherein X′ stands for a tetravalent organic group,

wherein Y stands for a hydrogen atom (H), a bromine atom (Br), achlorine atom (Cl), a fluorine atom (F), a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group.
 12. A method for theproduction of polyimide represented by the formula (10), which comprisescyclizing by heating the polyamic acid produced by the method set forthin claim 11:

wherein Y stands for a hydrogen atom (H), a bromine atom (Br), achlorine atom (Cl), a fluorine atom (F), a C₁-C₅ alkyl group optionallyhaving a substituent, or a C₁-C₅ alkoxyl group optionally having asubstituent, 1 is an integer in the range of 1-4, m is an integer in therange of 0-3, provided that the total number of 1 and m (1+m) is 4, andX′ stands for a tetravalent organic group.